1. Field of Invention
This invention relates to venting a tire during the molding process by penetration of the tire lower sidewall bead area by axially extending pins during closing of the mold and removal of the pins during opening of the mold without damaging the tire.
2. Description of the Related Art
Tire venting is necessary with certain tires such as those used for aircraft where the inflation pressures are very high. If the air does not have a path to escape it can become trapped inside the layers of the tires and cause separation of the components. One way of providing this venting is by stabbing the tires with an awl to provide vent holes for diffusion of the air out of the tires. This stabbing has been done manually and may cause inaccuracy in placement and depth of the vent holes.
In U.S. Pat. Nos. 2,031,560 and 2,047,858 hollow needles have been inserted through lateral passages in the tire mold to vent the tire during molding. The needles were hollow and inserted after the mold was closed on the tire. The needles were then removed before the mold was opened. This method is time consuming and is dependent on the hollow needles being maintained with open channels for releasing the air.
Another attempt to provide venting of a tire is described in U.S. Pat. No. 4,257,154 where elongated flexible air guides are inserted in the bead area of a tire after it is vulcanized. This involves using a threaded tool for use with an electric drill to install the air guides.
The present invention is directed to a method of providing vents in the bead area of a tire by penetration of the tire with axially extending pins mounted at spaced apart positions on the axially moveable mold components. This is accomplished with a conventional tire mold having axially moveable bead forming surfaces on which the pins are supported. The pins may be mounted on the sidewall mold plate or on the mold ring depending on the construction of the mold.
In accordance with one aspect of the invention there is provided a tire mold for vulcanizing a tire, having bead portions, the mold having mold halves with each of the mold halves having axially moveable mold components characterized by a plurality of vent forming pins mounted on at least one of the components at circumferentially spaced venting positions in a bead forming area and each of the pins extending in a generally axial direction into a tire forming cavity of the mold whereby the pins will penetrate the bead portions of the tire in the mold and form vents in the bead portions of the tire upon movement of the mold halves and the mold components together in an axial direction.
In accordance with another aspect of the invention, there is provided a method of molding axially extending vent holes in the bead areas of a tire in a tire mold having an upper mold half and a lower mold half, characterized by:
(a) providing axially extending pins on the upper mold half and on the lower mold half at spaced apart positions in a bead forming area of each mold half;
(b) placing a tire in the mold;
(c) closing the mold by moving the upper mold half and the lower mold half together in an axial direction causing the pins to penetrate the tire and form vents;
(d) applying heat under pressure to the tire in the mold;
(e) opening the tire mold by moving the mold halves apart in an axial direction; and,
removing the tire from the mold in an axial direction to withdraw the pins from the bead areas of the tire.
Still other benefits and advantages of the invention will become apparent to those skilled in the art to which it pertains upon a reading and understanding of the following detailed specification.